I have been eyeing the Epics on PE for a while. With those I know for sure there is no Klippel testing let alone the usage in production. These are a nice alternative and cheaper to boot. The box requirements are not low but I'm going to IB my subs anyway.

there's a huge Ultimax thread over on diyma. P.E. sent us one to try and personally for me it just didn't work in the mobile environment. I ended up going back to the 12" Dayton DVC in the car and the Ultimax ended up in an antique cedar chest build.

Never looked like it would work.... I looked at it for my studio-use sub but it still needed either an incredibly huge box or a lot of EQ and power... I prefer natural gain and not as much EQ phase shift.